氧化铜光电化学分解水反应速率方程

doi:10.61558/2993-074X.3467

摘要/Abstract

摘要：

P型半导体光催化分解水是一种非常有前景的制氢方法。尽管对其反应动力学进行了很多研究并取得了不少进展，但建立其速率方程鲜见文献报道。本文采用积分电量和电化学阻抗谱等多种电化学方法研究了典型p型半导体氧化铜（CuO）光电化学分解水时光生电荷浓度、界面电荷转移速率常数及其与反应速率（光电流表示）之间的关系，力图建立其速率方程。结果表明，电极界面电荷转移速率常数与光生电荷浓度指数相关，光电流等于此速率常数乘以光生电荷浓度，反应级数（以光生电荷计）为一级，不同于常规化学反应速率方程和类似文献报道结果。这种光生电荷浓度相关的电荷转移速率常数主要是由于光生电荷在表面态中积累导致费米能级钉扎（伽伐伲电位是反应主要驱动力）和/或Frumkin行为（化学位是反应主要驱动力）引起。我们认为，该速率方程的建立对进一步研究CuO光电极析氢反应机理和设计CuO基高性能光催化剂具有指导意义。

关键词: 氧化铜, 光电化学分解水, 电化学阻抗谱, 速率方程, 光生载流子动力学

Abstract:

Photocatalytic splitting of water over p-type semiconductors is a promising strategy for production of hydrogen. However, the determination of rate law is rarely reported. To this purpose, copper oxide (CuO) is selected as a model photocathode in this study, and the photogenerated surface charge density, interfacial charge transfer rate constant and their relation to the water reduction rate (in terms of photocurrent) were investigated by a combination of (photo)electrochemical techniques. The results showed that the charge transfer rate constant is exponential-dependent on the surface charge density, and that the photocurrent equals to the product of the charge transfer rate constant and surface charge density. The reaction is first-order in terms of surface charge density. Such an unconventional rate law contrasts with the reports in literature. The charge density-dependent rate constant results from the Fermi level pinning (i.e., Galvani potential is the main driving force for the reaction) due to accumulation of charge in the surface states and/or Frumkin behavior (i.e., chemical potential is the main driving force). This study, therefore, may be helpful for further investigation on the mechanism of hydrogen evolution over a CuO photocathode and for designing more efficient CuO-based photocatalysts.

Key words: CuO, Photoelectrochemical water splitting, Electrochemical impedance spectroscopy, Rate law, Kinetics of photogenerated carriers

高博远, 冷文华. 氧化铜光电化学分解水反应速率方程[J]. 电化学（中英文）, 2024, 30(8): 2312111.

Bo-Yuan Gao, Wen-Hua Leng. Rate Law for Photoelectrochemical Water Splitting over CuO[J]. Journal of Electrochemistry, 2024, 30(8): 2312111.

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链接本文: https://electrochem.xmu.edu.cn/CN/10.61558/2993-074X.3467

https://electrochem.xmu.edu.cn/CN/Y2024/V30/I8/2312111

图/表 7

参考文献 28

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Applied potential/V_SCE	CuO electrode
0.10	$\begin{array}{l}J_{\mathrm{ph}}=-3.66 \times \exp \left(0.50 \times\left[e_{s}\right]\right) \times\left[e_{s}\right]\end{array}$	$J_{\mathrm{ph}}=-0.40 \times \exp \left(0.83 \times\left[e_{\mathrm{s}}\right]\right) \times\left[e_{\mathrm{s}}\right]$
-0.02	$\begin{aligned}J_{\mathrm{ph}}=-10.63 \times & \exp \left(0.17 \times\left[e_{s}\right]\right) \\& \times\left[e_{s}\right]\end{aligned}$	$J_{\mathrm{ph}}=-8.60 \times \exp \left(0.14 \times\left[e_{\mathrm{s}}\right]\right) \times\left[e_{\mathrm{s}}\right]$
-0.14	$\begin{aligned}J_{\mathrm{ph}}=-37.92 \times & \exp \left(0.017 \times\left[e_{s}\right]\right) \\& \times\left[e_{\mathrm{s}}\right]\end{aligned}$	$\begin{aligned}J_{\mathrm{ph}}=-11.76 \times & \exp \left(0.19 \times\left[e_{\mathrm{s}}\right]\right) \\& \times\left[e_{\mathrm{s}}\right]\end{aligned}$